I think you jumped the gun by taking the engine out with a budget of 500.00. The easiest thing at this point is maybe to put it back in the truck for further diagnostics. I would start by taking out all the spark plugs and doing a compression test, you may want to give each cylinder a squirt of motor oil. Then I'd make sure I have power to the + terminal on the coil. Then check to see if you have spark at the spark plugs while turning the motor over. If the compression is reasonable and you have spark move forward and see if you have fuel to the carburetor. If the truck has been sitting I would use a remote gas can. I would also get a carburetor kit and take the carburetor apart, soak it and assemble with the new kit. If all the above work there is no reason it shouldn't run.